Enhanced recovery of alcohol from an ether containing stream

Abstract

A process for producing ethyl tertiary butyl ether and for the substantially complete recovery by fractional distillation of the unreacted ethanol contained in an etherification reaction zone product stream as a product along with the ethyl tertiary butyl ether reaction product. This process utilizes methanol as a fractionator feed additive to enhance the recovery of ethanol as a bottoms product.

That which is claimed is: 
     
       1. A method for producing ethyl tertiary butyl ether (ETBE), said method comprises the steps of: reacting a stream containing isobutylene, ethanol and non-reactive reactive hydrocarbons within an etherification reaction zone to form a reaction product containing ETBE, ethanol, and non-reactive hydrocarbons;   adding a methanol stream containing methanol to said reaction product to give a fractionator feed such that the molar ratio of methanol to ethanol in said feed is in the range of from about 0.1:1 to about 10:1; and   separating by fractionation said feed into an overhead stream and a bottoms stream, said overhead stream containing methanol and non-reactive hydrocarbons and said bottoms stream containing ETBE and ethanol.   
     
     
       2. A method as recited in claim 1, further comprising: contacting said overhead stream with a water stream containing water within an extraction zone to thereby extract methanol from said overhead stream and providing a methanol lean raffinate stream containing non-reactive hydrocarbons and a methanol rich extract stream; and   separating said methanol rich extract stream into said water stream and said methanol stream.   
     
     
       3. A method as recited in claim 1, wherein at last 70 weight percent of the ethanol in said reaction product is contained in said bottoms stream. 
     
     
       4. A method as recited in claim 3 whereto said reaction product has a concentration of methanol of less than 1 weight percent. 
     
     
       5. A method as recited in claim 4 wherein said overhead stream has a concentration of ethanol of less than 1 weight percent. 
     
     
       6. A method as recited in claim 5 whereto said methanol stream has a concentration of methanol exceeding 90 weight percent. 
     
     
       7. A method as recited in claim 2 wherein said methanol lean raffinate stream has a concentration of alcohol less than 1 weight percent. 
     
     
       8. A method as recited in claim 7 wherein said reaction product has a concentration of methanol of less than 1 weight percent. 
     
     
       9. A method as recited in claim 8 whereto said overhead stream has a concentration of ethanol of less than 1 weight percent. 
     
     
       10. A method as recited in claim 9 whereto said methanol stream has a concentration of methanol exceeding 90 weight percent. 
     
     
       11. A method for improving the recovery of ethanol contained in an etherification reaction zone product stream containing ethyl tertiary butyl ether (ETBE), ethanol and hydrocarbons, said method comprises the steps of: providing a concentration of methanol in said etherification reaction zone product stream such that the molar ratio of methanol to ethanol is in the range of from 0.1:1 to about 10:1; and   thereafter separating by fractionation said etherification reaction zone product stream into an overhead stream, containing methanol and hydrocarbons, and a bottoms stream containing ETBE and ethanol.   
     
     
       12. A method as recited in claim 11 wherein at least 70 weight percent of the ethanol in said etherification reaction zone product stream is contained in said bottoms stream. 
     
     
       13. A method as recited in claim 12 wherein said concentration of methanol provided in said etherification reaction zone product stream is such that the molar ratio of methanol to ethanol is in the range of from about 0.25:1 to about 7.5:1. 
     
     
       14. A method as recited in claim 13 wherein said etherification reaction zone product stream has a concentration of methanol less than 1 weight percent prior to providing said concentration of methanol. 
     
     
       15. A method as recited in claim 14 wherein said overhead product has a concentration of ethanol less than 1 weight percent. 
     
     
       16. A method as recited in claim 15 wherein at least 95 weight percent of the ethanol in said etherification reaction zone product stream is contained in said bottoms stream.